ui: Adding fields validation in addHost form

1. For root password during provisioning host
2. For empty  compute resources and host group lists, when discovered host is
 added.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1127606
Change-Id: Icfc3e500ad06728fc8c410baa13405633fc90da2
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>